The invention relates to spacer-expanders for spacing and positioning two oil control rails in a piston ring groove of a piston for an internal combustion engine.
When a piston of an internal combustion engine or compressor is reciprocating within an associated cylinder it is essential that a lubricant such as oil is provided between the piston and piston rings and the cylinder. The consumption of lubricant is increased, however, if the lubricant is, for example, allowed to reach the combustion chamber. For this reason it has become customary to provide a scraper ring located in a piston ring groove and extending around the piston. Such a ring includes two rails which engage the associated cylinder wall and remove lubricant from the cylinder wall to prevent the passage of lubricant past the rails to the combustion chamber.
To operate successfully it is necessary that the rails of the ring are urged both towards the cylinder wall, to seal against the cylinder wall, and towards radially extending walls of the piston ring groove, to prevent lubricant seeping around the groove and the rails. It is also desirable that the rails are not permitted to flex unduly in a radialy direction as a result of the forces generated by the sliding contact between the ring or rings and the cylinder wall.